The prior art includes various shoe constructions in which a spring is applied to a shoe sole for shock absorption, and energy return during walking or running. Examples of these designs include that shown in U.S. Pat. No. 4,843,737 to Vorderer, in which two outwardly curved plates having a tensioning spring are placed in the heel of an athletic shoe, to store and return energy to a runner while providing shock absorption. U.S. Pat. No. 4,815,221 to Diaz discloses a shoe sole having an energy control system located in a cavity of the sole, which comprises a set of spring strips and an overlying energy absorbing member capable of absorbing impact energy.
In U.S. Pat. No. 4,774,774 to Allen, a shoe sole structure is disclosed comprising a plurality of vertically stacked disc-springs spanning the width and length of the sole to form a honeycomb framework which applies energy to the base of the foot upon release after load compression. A spring boot for bouncing and exercise is disclosed in U.S. Pat. No. 4,660,299 to Omilusik, wherein a set of four coil springs is attached to the underside of a boot.
U.S. Pat. No. 4,506,460 to Rudy describes a spring-type moderator in combination with an air-cushioned sole in an athletic shoe providing improved shock absorption and energy return. A hopping and dancing shoe is described in U.S. Pat. No. 4,457,084 to Horibata, et. al., comprising a shoe sole and two coil springs attached on its underside by bolts and nuts. In a similar design, U.S. Pat. No. 4,196,903 to Illustrato discloses a pair of jog-springs attached to the underside of a shoe sole providing a soft, bouncing action in use. In U.S. Pat. No. 3,777,374 to Hendricks, a pleasure shoe is disclosed having a compression spring unit fitted into a shoe heel for providing shock absorption.
A shoe having a sole element provided with bores for retaining resilient means such as spring elements is disclosed in U.S. Pat. No. 2,710,460 to Stasinos. In U.S. Pat. No. 2,437,227 to Hall, a cushioned shoe sole is disclosed comprising a cushioning layer composed of resilient material with coil springs molded therein, and placed between top and bottom facing sheets.
As is well known, the feet, and particularly the soles of the feet, carry the entire body weight. The many shoe sole constructions found in the market absorb only a small portion of the shock caused as the shoe contacts the floor, and shocks which are not absorbed cause damage to the body. This occurs in the soles of the feet, which have many bones and many jointed surfaces, and in the knees which have fine miniscus stabilizing the joints and permitting smooth movement. The spinal cord is built from many vertebrae, with discs between them which are very sensitive to changes, and which permit bending and straightening of the body.
Over a long period of walking, the beating and shocks imparted to the soles of the feet may cause stress fractures in the legs. Also, these shocks cause changes in the structure of the vertebrae, affecting the discs between them, by making them thin and irregular due to friction, so that they lose their flexibility. This damage causes limited movement and flexibility for the entire length of the spinal cord, leading to neck and shouder pain, poor blood circulation, and stability problems.
The effects of the damage to the discs are felt frequently in back pain, along with a tendency for increased fatigue, and over time the growth of bone fibers is expected in the area around the vertebrae. Sometimes this brings about a split in the disc as it explodes under pressure to its soft center. Damage to the discs of the vertebrae can also cause distortion in straightness of the back which brings about pressure on nerves and may cause a neurological block leading to paralysis. In addition, problems including headaches, dizziness and deadening of the senses cause major day-to-day discomforts.
In order to solve these and other related problems, and to address the needs of individual users whose requirements vary, there is a need to provide an improved system of shock absorption which is user-specific and preserves the maximum amount of energy accumulating during compression of the material from which the sole is constructed, reducing wastage by friction or heat, enabling maximum energy to be returned after compression.